Systematic review of the efficiency of photocatalytic processes for doxycycline antibiotic removal from aqueous media

The use of antibiotics, such as doxycycline (DOX), has caused chronic contamination of aquatic systems and a high probability of antimicrobial resistance. Traditional wastewater treatment methods typically fail to fully treat these compounds. Heterogeneous photocatalysis can be used to degrade and mineralize pharmaceutical contaminants in water using advanced oxidation processes. This systematic review analyzed the efficacy of photocatalytic systems for removing DOX from water. 37 studies were identified using the selection criteria. The operational parameters included catalyst loading, solution pH, initial DOX concentration, light source, and reaction kinetics. Degradation mechanisms and the role of reactive species are discussed here. Analysis of the 37 included studies revealed high remediation potential, with Doxycycline removal efficiencies ranging from 69 to 100% within 15 to 360 min of irradiation. The majority of advanced heterojunction systems achieved > 90% degradation. Unlike previous reviews, this study identifies a critical Concentration Gap where laboratory successes at high DOX levels (10–50 mg/L) fail to predict performance at environmentally relevant trace concentrations (ng/L). Photocatalysis is an efficient and sustainable method for removing DOX. Future studies should focus on upscaling laboratory to pilot-level reactor designs, as well as the stabilization of catalysts and their recovery, to provide a mechanism for industrial use of the technology.